1. Description of the Prior Art
Prior art semiconductor diodes using glass fused directly to the semiconductor portion of the diode for purposes of protecting the PN junction have been limited to relatively small low current diodes. An example of such a diode is type UT4005 manufactured and sold by the Unitrode Corporation. It is also known in the prior art to encapsulate semiconductor devices in thermosetting resinous insulating material. Examples of devices hermetically sealed diodes using resinous materials are disclosed in U.S. Pat. Nos. 3,475,662; 3,476,987 and 3,476,988 as well as 3,486,084.
2. Summary of the Invention
The diode which is the subject of this invention utilizes a body of semiconductor material which includes a PN junction formed by P and N regions respectively extending from the PN junction to opposed substantially flat major surfaces of the body of semiconductor material. The area of the PN junction is coextensive with the area of the body of semiconductor material. That is, the junction extends entirely across the body and terminates at an edge portion of the body. The edge portion of the body extending from one major surface to the other. Electrodes are affixed to the opposed major surfaces of the body of semiconductor material by soldering, brazing or any other suitable techniques known to those skilled in the art. The area of each of the electrodes is substantially coextensive with the area of the surface of the body of semiconductor material to which they are affixed. The body of semiconduct material and the electrodes affixed thereto are for convenience referred to as a fusion.
The fusion is encircled by an annular or ringshaped glass member having inner and outer surfaces. The inner surface of the annular-shaped glass member is fused to the edge of the body of semiconductor material to form a seal protecting the PN junction. An annular or ring-shaped metallic member having inner and outer surfaces, encircles the annular-shaped glass member with the outer surface of the annular-shaped glass member fused to the inner surface of the annular-shaped metallic member. In the preferred embodiment the glass for the annular-shaped glass member and the metal for the annular-shaped metallic member are selected such that the annular metallic member maintains the annular glass member in compression for normal temperature operating ranges of the diode. The glass for the annular-shaped glass member must also be substantially alkaline-free to prevent contamination of the PN junction.